Why not, why not, WHY NOT!!!!!!
We're going to have Jeimer for two years, his age 28 and 29 season, and given that our horizon to return to serious contention is probably three years, I don't think it would be a terrible idea to lock him up for that third year versus him leaving because we won't accede to his demands for multiple years at age thirty, with our having to start all over at 3B. Because if he's above average in 2022 and 2023, he's not going to come back on a mere one-year contract as a free agent. At that point, the deal to keep him would have to be years and years.
I wouldn't want to guarantee anything to Jeimer beyond that right now, but I think a three-year deal with discretionary team options to take him through age 31 or 32 wouldn't be a terrible risk, and at more favorable money than if he were to have any All-Star seasons in the next two years. Despite that we've basically drafted or traded for just about every position player as a third baseman in the past few years, it's not as though we have anyone projected to be as good as he is banging on the door to take his job away anytime soon.
All this said, I don't have strong feelings about it. I'd also be fine with letting him play his final two arb years and then taking our chances on the system or the market. But if the Tigers' preference is to boot Jeimer after two years no matter what, then not extending him is probably the right non-move.